Polyoxymethylene compositions

ABSTRACT

Polyoxymethylene compositions, articles comprising these compositions, and processes of making the compositions, comprising: a) at least one polyoxymethylene polymer; b) about 0.1 to about 5 wt. % of poly alpha-1,3-glucan having a d90 particle size of 50 microns or less; c) optionally, at least one additive selected from the group consisting of nucleating agents, waxes, ultraviolet stabilizers, colorants, antioxidants, formaldehyde scavengers, lubricants, and mixtures of these; wherein an article molded from said polyoxymethylene composition exhibits a formaldehyde emission of 1 weight percent or less when measured according to TEF test method.

OVERVIEW

Described herein are thermally stabilized polyoxymethylene compositionsthat exhibit, in the melt state, formaldehyde emissions of less than 1weight percent.

Polyoxymethylene (POM, also known as polyacetal) compositions exhibittribology, hardness, stiffness, toughness, coefficient of friction,solvent resistance, and the ability to crystallize rapidly that areparticularly suitable to produce articles for demanding uses. However,during melt-processing, polyoxymethylenes can thermally degrade andrelease formaldehyde. Formaldehyde evolution, measured as thermallyevolved formaldehyde (TEF), is an indirect measure of the heat stabilityof POM compositions.

Effort is frequently given to methods of reducing formaldehyde emissionsin POM compositions during processing and/or from articles produced fromthe POM compositions. In particular, such efforts include adding one ormore ingredients to POM compositions to reduce formaldehyde emissions,improve creep properties, impact resistance, etc. of the resultantarticle. Additives known to improve one property may reduce anotherproperty, so combining additives have recognized limitations. Improvingformaldehyde emission can be achieved by adding formaldehyde scavengerssuch as allantoin compounds to POM compositions. However, addition ofallantoin to POM compounds may reduce other physical properties, such ascreep, which is undesirable.

U.S. Pat. No. 5,011,890 discloses POM compositions that contain polymershaving formaldehyde reactive nitrogen groups such as polyacrylamide.U.S. Pat. No. 5,106,888 discloses polyacetal compositions that containmicrocrystalline cellulose (MCC) as a thermal stabilizer with polyamide.U.S. Pat. No. 6,642,289 discloses POM compositions that contain anallantoin compound and optionally a basic nitrogen-containing compoundand/or an antioxidant that contributes to stability, particularly heatstability, of polyacetal resins and suppression of formaldehydeemission.

Needed are polyoxymethylene compositions that, when in the melt state,exhibit a formaldehyde emission of less than 1 weight percent.

DETAILED DESCRIPTION Definitions

As used herein, the terms “a”, “an” refers to one, more than one and atleast one and therefore does not necessarily limit its referent noun tothe singular.

When these terms refer to a non-exclusive inclusion, a process, method,article, or apparatus that comprises a list of elements is not limitedto the listed elements but may include other elements not expresslylisted or which may be inherent. Further, unless expressly stated to thecontrary, “or” refers to an inclusive, not an exclusive, or. Forexample, a condition A or B is satisfied by any one of the following: Ais true (or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

As used herein, the term “article” refers to an unfinished or finisheditem, thing, object, or an element or feature of an unfinished orfinished item, thing or object. As used herein, when an article isidentified as unfinished, the term “article” may refer to any item,thing, object, element, device, etc. that will be included in a finishedarticle and/or will undergo further processing in order to become afinished article.

An article may comprise one or more element(s) or subassembly(ies) thateither are partially finished and awaiting further processing orassembly with other elements/subassemblies that together will comprise afinished article.

As used herein, the terms “polyoxymethylene” and “polyacetal” includeshomopolymers of formaldehyde or of cyclic oligomers of formaldehyde, theterminal groups of which are end-capped by esterification oretherification, and co-polymers of formaldehyde or of cyclic oligomersof formaldehyde and other monomers that yield oxyalkylene groups with atleast two adjacent carbon atoms in the main chain, the terminal groupsof which co-polymers can be hydroxyl terminated or can be end-capped byesterification or etherification.

As used herein, the term “nucleating agent” refers to any particulatematerial that nucleates polyoxymethylene. The nucleating agent can beorganic or inorganic and has an average particle size of 100 microns orless.

As used herein, the term “formaldehyde scavenger” refers to any organiccyclic compound having an active imino group which has a high capacityto form a methylol group by reacting with formaldehyde.

As used herein, the term “antioxidant” refers to a monocyclic hinderedphenol compound, a polycyclic hindered phenol compound bonded by ahydrocarbon group or a group containing sulfur atom, and a hinderedphenol compound having an ester group or amide group.

As used herein, the term “melt flow rate” or “melt index” refers to ameasure of the flow of a thermoplastic polymer in the melt and isdefined as the mass of polymer, in grams, flowing in ten minutes througha capillary of a specific diameter and length at a certain pressure andtemperature measured according to ISO 1133. Melt flow rate is anindirect measure of the molecular weight of a polymer.

As used herein, the term “melt state” or “in the melt state” refer to apolyoxymethylene composition which has been heated to its melting pointor above its melting point.

As used herein, the term “emitted formaldehyde” or “formaldehydeemission” refers to that formaldehyde which evolves frompolyoxymethylene compositions while in the melt state as measuredaccording to the TEF test method and recorded as weight percentformaldehyde.

Ranges

Any range set forth herein includes its endpoints unless expresslystated otherwise. Setting forth an amount, concentration, or other valueor parameter as a range specifically discloses all ranges formed fromany pair of any upper range limit and any lower range limit, regardlessof whether such pairs are separately disclosed herein. To the point, theranges in the compositions and articles described herein are not limitedto specific pairs of upper and lower limits disclosed in thedescription.

Preferred Variants

The setting forth of variants in terms of materials, methods, steps,values, ranges, etc.—whether identified as preferred variants or not—ofthe compositions and articles described herein is specifically intendedto disclose any composition and article that includes any combination ofsuch materials, methods, steps, values, ranges, etc. Such combinationsare specifically intended to be preferred variants of the compositionsand articles described herein.

Abbreviations

As used herein, “weight percent” is abbreviated as “wt %”.

As used herein, “polyoxymethylene” is abbreviated as “POM”.

As used herein, “grams per minute” is abbreviated as “g/min”.

Generally: Compositions Described Herein

Disclosed herein are polyoxymethylene compositions that, when in themelt state, exhibit a formaldehyde emission of 1 weight percent or less,preferably 0.6 weight percent or less. It has surprisingly been foundthat when a specific polysaccharide based material is added to thepolyoxymethylene composition, the formaldehyde emissions issignificantly reduced relative to polyoxymethylene composition lackingsaid polysaccharide based material.

Specifically disclosed herein are polyoxymethylene compositionscomprising:

-   -   a) at least one polyoxymethylene polymer;    -   b) about 0.1 to about 5 wt. % of poly alpha-1,3-glucan;    -   c) optionally, at least one additive selected from the group        consisting of nucleating agents, waxes, ultraviolet stabilizers,        colorants, antioxidants, formaldehyde scavengers, lubricants,        and mixtures of these;        wherein said polyoxymethylene composition exhibits a        formaldehyde emission of 1 weight percent or less when measured        according to the TEF test method; and wherein said particle size        is measured according to ISO 13320:2009.

Also disclosed herein are articles made of these compositions andprocesses of making the compositions and articles.

Further disclosed herein are processes of making a polyoxymethylenecomposition comprising the step of mixing:

-   -   a) at least one polyoxymethylene polymer;    -   b) about 0.1 to about 5 wt. % of poly alpha-1,3-glucan having a        d90 particle size of 50 microns or less measured according to        ISO 13320:2009;    -   c) optionally, at least one additive selected from the group        consisting of nucleating agents, waxes, ultraviolet stabilizers,        colorants, antioxidants, formaldehyde scavengers, lubricants,        and mixtures of these;        to prepare a polyoxymethylene composition,        wherein said polyoxymethylene composition exhibits a        formaldehyde emission of 1 weight percent or less when measured        according to the TEF test method.

a) Polyoxymethylene (POM) Polymer

The polyoxymethylene (also known as polyacetal) in the compositionsdescribed herein may be one or more homopolymers, copolymers, ormixtures of these. Homopolymers are prepared by polymerizingformaldehyde or formaldehyde equivalents, such as cyclic oligomers offormaldehyde.

Copolymers may contain one or more co-monomers generally used inpreparing polyoxymethylene compositions, which include acetals andcyclic ethers that lead to the incorporation into the polymer chain ofether units with 2-12 sequential carbon atoms. If a copolymer is used inthese compositions, the quantity of co-monomer will not be more than 20weight percent, preferably not more than 15 weight percent, and mostpreferably about two weight percent. Preferable comonomers are1,3-dioxolane, ethylene oxide, and butylene oxide, where 1,3-dioxolaneis more preferred, and preferable polyoxymethylene copolymers arecopolymers where the quantity of co-monomer is about 2 weight percent.

It is also preferred that the homo- and copolymers are: 1) homopolymerswhose terminal hydroxy groups are end-capped by a chemical reaction toform ester or ether groups; or, 2) copolymers that are not completelyend-capped, but that have some free hydroxy ends from the co-monomerunit or are terminated with ether groups. Suitable end groups forhomopolymers are acetate and methoxy and preferred end groups forcopolymers are hydroxy and methoxy.

The polyoxymethylene used in the compositions described herein may bebranched or linear and generally have a number average molecular weightof at least 10,000, preferably 20,000-90,000. The molecular weight maybe conveniently measured by gel permeation chromatography in m-cresol at160° C. using a DuPont PSM bimodal column kit with nominal pore size of60 and 1000 angstrom. The molecular weight may also be measured bydetermining the melt flow using ASTM D1238 or ISO 1133. The melt flowwill be in the range of 0.1 to 100 g/10 min, preferably from 0.5 to 100g/10 min, more preferably from 2 to 60 g/10 min, and most preferablyfrom 2 to 40 g/10 min for injection molding purposes.

The amount of POM in these compositions ranges from about 85 to about99.9, preferably from 90 to 99.5, more preferably from 97 to 99, andmost preferably from 98 to 99.5 weight percent of the total weight ofthe composition.

b) Poly alpha-1,3-glucan

Component (b) in the polyoxymethylene compositions described herein ispoly alpha-1,3-glucan. Poly alpha-1,3-glucan is a polymer comprisingglucose monomeric units linked together by glycosidic linkages, whereinat least about 50% of the glycosidic linkages are alpha-1,3-glycosidiclinkages. Poly alpha-1,3-glucan is a type of polysaccharide. The1,3-linkage of the poly alpha-1,3-glucan can be illustrated as followswherein n is an integer of at least 6 or more:

The poly alpha-1,3-glucan in the polyoxymethylene compositions describedherein is a solid having a particle size of from about 50 to 0.1microns, preferably from 25 to 0.5 microns, and more preferably from 10to 0.5 microns when measured according to ISO 13320:2009. Mostpreferably the poly alpha-1,3-glucan particles in the polyoxymethylenecompositions described herein have a d90 of less than 50 microns.

The poly alpha-1,3-glucan described herein can be prepared by extractingit from various organisms, such as fungi, that produce polyalpha-1,3-glucan. Alternatively, poly alpha-1,3-glucan can beenzymatically produced from sucrose using one or moreglucosyltransferase (gtf) enzymes (e.g., gtfJ), such as described inU.S. Pat. Nos. 7,000,000 and 9,139,718, both of which are incorporatedherein by reference.

The concentration of poly alpha-1,3-glucan in the polyoxymethylenecompositions described herein may range from about 0.1 to 20 weightpercent, preferably from 0.2 to 15 weight percent, and more preferablyfrom about 0.2 to 1 weight percent.

c) Additives

Optional additives which may be added to the polyoxymethylenecompositions described herein include any material which does notincrease the formaldehyde emissions of the polyoxymethylene compositionabove 1 weight percent when measured according to the TEF test.

Examples of such additives include nucleating agents, waxes, ultravioletstabilizers, colorants, antioxidants, formaldehyde scavengers,lubricants, and mixtures of these.

Examples of nucleating agents include any particulate material thatnucleates polyoxymethylene. Preferably, the nucleating agent is selectedfrom titanium oxides, boron compounds, such as boron nitride, silica,silicates, montmorillonite, calcium carbonate, valentinite,pyrophyllite, dolomite, organic or inorganic pigments,melamine-formaldehyde condensates, phyllosilicates, talc, powderedsulfates or carbonates, terpolymers of trioxane, and ethylene oxide andbutanediol diglycidyl ethers. Preferred nucleating agents include talc,boron nitride and terpolymers of trioxane. The nucleating agent may havean average particle size of 100 microns or less, preferably 10 micronsor less, more preferably 5 microns or less, and most preferably 1 micronor less. When used, the amounts of nucleating agent in thepolyoxymethylene compositions ranges from 0.01 to 0.9, preferably from0.01 to 0.7, more preferably from 0.02 to 0.5, and most preferably from0.02 to 0.4 weight percent of the total weight of the polyoxymethylenecomposition.

Examples of optional formaldehyde scavengers which may be used in thepolyoxymethylene compositions include organic cyclic compounds having anactive imino group. Examples of organic cyclic compounds having anactive imino group include hydantoins and imidazole compounds such ashydantoin, dimethylhydantoin (e.g., 5,5-dimethylhydantoin) andallantoin. When used, the amount of formaldehyde scavenger in thepolyoxymethylene compositions ranges from 0.01 to 0.5, preferably from0.03 to 0.4, more preferably from 0.05 to 0.4, and most preferably from0.1 to 0.3 weight percent of the total weight of the composition.

Examples of antioxidants which may be used in the polyoxymethylenecompositions described herein include hindered phenol-basedantioxidants. The hindered phenol-based antioxidants include amonocyclic hindered phenol compound, a polycyclic hindered phenolcompound bonded by a hydrocarbon group or a group containing sulfuratom, and a hindered phenol compound having ester group or amide group.Preferred examples of hindered phenol antioxidant compounds includepentaerythrityltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox1010), triethylene glycolbis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (Irganox 245),3,3′-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionohydrazide](Irganox MD 1024), hexamethylene glycolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 259),N,N′-(Hexane-1,6-diyl)bis(3,5-di-tert-butyl-4-hydroxybenzenepropanamide)(Irganox 1098) and 3,5-di-tert-butyl-4-hydroxytoluene (Lowinox BHT).Preferred hindered phenol antioxidants are Irganox 1010, Irganox 245,Irganox 1098 or combinations of these. When used, the amount ofantioxidant in the polyoxymethylene compositions ranges from 0.02 to0.5, preferably from 0.05 to 0.4, more preferably from 0.1 to 0.4, andmost preferably from 0.1 to 0.3 weight percent of the total weight ofthe polyoxymethylene composition.

Suitable lubricant additives include silicone lubricants such asdimethylpolysiloxanes and their derivatives; oleic acid amides; alkylacid amides. Other suitable additives include non-ionic surfactantlubricants; hydrocarbon waxes; chlorohydrocarbons; fluorocarbons;oxy-fatty acids; esters such as lower alcohol esters of fatty acids;polyvalent alcohols such as polyglycols and polyglycerols; and metalsalts of fatty acids, such as lauric acid and stearic acid. Suitableultraviolet light stabilizers include benzotriazoles, benzophenones,aromatic benzoates, cyano acrylates, and oxalic acid anilides.

Properties of Polyoxymethylene Compositions Described Herein

Polyoxymethylene compositions are used in the manufacture of moldedarticles, such as gears, safety restraint parts, and especially for usein automotive applications. During manufacture of articles prepared fromthese polyoxymethylene compositions, formaldehyde may be released,especially when high temperatures are required during manufacture ofarticles. Because formaldehyde is labeled as a carcinogen in manycountries, such formaldehyde emissions are undesirable. Efforts toreduce formaldehyde emissions include adding one or more ingredients topolyoxymethylene compositions to reduce formaldehyde emissions.

The polyoxymethylene compositions described herein exhibit a surprisingdecrease in formaldehyde emissions compared to polyoxymethylenecompositions not comprising poly alpha-1,3-glucan. When polysaccharidessuch as amylopectin are added to the polyoxymethylene compositionsdescribed herein, the formaldehyde emissions are considerably higherthan when poly alpha-1,3-glucan is used.

It has also been surprisingly found that when the particle size of thepoly alpha 1,3-glucan is less than about 50 microns, the formaldehydeemissions are less than about 1 wt % TEF. When the poly alpha-1,3-glucanparticle size is greater than about 50 microns, the formaldehydeemissions are greater than 1 wt % TEF.

Methods of Making the Compositions Described Herein

The polyoxymethylene compositions described herein may be made bymelt-blending the components using any known methods. The componentmaterials may be mixed to homogeneity using a melt-mixer such as asingle or twin-screw extruder, blender, kneader, Banbury mixer, etc. togive a resin composition. Or, part of the materials may be mixed in amelt-mixer, and the rest of the materials may then be added and furthermelt-mixed until homogeneous. When adding the components in a stepwisefashion, part any component and any other component may be first addedand melt-mixed with the remaining components and further melt-mixeduntil a well-mixed composition is obtained. The melt-mixing can resultin pellets, which can be extruded or molded into articles.

Articles Comprising the Compositions Described Herein

The compositions described herein may be molded into articles using anysuitable melt-processing technique known in the art, such as injectionmolding, extrusion molding, blow molding, and injection blow molding.Injection blow molding and injection molding are more preferred withinjection molding most preferred. In addition, these compositions may beformed into films and sheets by extrusion to result in either castand/or blown films. Such sheets may be further thermoformed intoarticles and structures that may be oriented from the melt or at a laterstage in processing.

These compositions may also be used to form fibers and filaments thatmay be oriented from the melt or at a later stage in processing.Articles comprising these compositions include, without limitation,gears, toys, cigarette lighter bodies, writing pen bodies, conveyor beltparts, safety restraint parts, car interior parts, automotive fasteners,retractors, sliding members, snap-fit buckles, and zippers.

Examples

The exemplary compositions identified by “E” in the tables below areintended only to further illuminate and not to limit the scope ofcompositions, methods, and articles described and recited herein.Comparative examples are identified in the tables below by “C”.

Materials

In the compositions listed in the tables below, the following materialswere used: POM—: Delrin® 500 acetal homopolymer having a melt flow index(190° C.; 2.16 kg. ISO 1133) of 12 g/10 min., available from E.I. DuPontde Nemours and Company, Wilmington, Del., USA [DuPont].

Amide polymer: a polyacrylamide thermal stabilizer available as MAP1070, a 20 weight percent polyethylene glycol coated polyacrylamide.Polyamide: PA 66/610/6 polyamide terpolymer (33/23/43 mol %) is athermal stabilizer with melting point of 150-160° C. and is ground priorto compounding to pass a 20 MESH screen.EVA: An ethylene vinyl alcohol copolymer comprising 29 mole percentethylene available as Soarnol™ D from Nippon Gohsei.Amylopectin: available from MP Biomedicals, LLC, Solon OH, USA[CAS#9037-22-3]Poly alpha-1,3-glucan: Enzymatically produced from sucrose using one ormore glucosyltransferase (gtf) enzymes (e.g., gtfJ). Prepared accordingto example 6 of U.S. Pat. No. 9,080,195 using a gtfJ enzyme. This polyalpha-1,3-glucan was then ground cryogenically in various particle sizesand used in the examples and comparative examples as Glucan A to C.Glucan A: d90 particle size less than 10 micronsGlucan B: d90 particle size less than 45 micronsGlucan C: d90 particle size less than 180 micronsSoarnol A: ethylene vinyl alcohol polymer (56 mol % vinyl alcohol) fromNippon Gohsei Antioxidant: Irganox 245 available from BASFLubricant: ethylene bisstearamide available as Acrawax C from LonzaChemicals MC-1: Microcrystalline Cellulose 1 having a particle size ofless than 50 microns (d90) available as Grinsted® MCC powder from DupontNutrition and Health, Wilmington, Del., USAMC-2: Microcrystalline Cellulose 2 having particle size greater than 40%200 mesh (about 75 microns) available as MCC powder from Sigma Aldrich

Methods

In the compositions listed in the tables below, the following methodswere used:

Melt Flow Rate

Melt Flow Index or Melt Flow Rate was determined using ISO 1133 andreported as grams/10 minute (190° C.; 2.16 kg.).

Particle Size

Particle Size Distribution (PSD) was measured using a MalvernMastersizer 2000 (Malvern Instruments, Westborough MA) Laser Diffractiondevice to which was attached a Malvern Sirocco dry powder disperser unitaccording to ISO 13320:2009, (Particle size analysis—Laser diffractionmethods”). The powder test sample was loaded into the Sirocco'svibratory feeder and dispersed in an air stream with a pressure settingof 2 bar. The dispersed powder was transported through the Mastersizerby the air stream. Particle size distribution is a volume-weighted sizedistribution and the results include the mass median size (d50) as wellas the 10^(th) (d10) and 90th (d90) percentiles of the PSD.

For example, a sample having a particle size of less than 60 micronsindicates that 90 percent of the particles have a particle size of lessthan 60 microns and is recorded as d90 less than 60.

Formaldehyde Emissions

Formaldehyde emissions or thermally emitted formaldehyde from articlesformed from the polyoxymethylene compositions described herein aredetermined according to the following TEF test procedure. The TEF testmethod has been tailored to determine formaldehyde emissions ofpolyoxymethylene compositions in the melt state.

The melt stability of the polyoxymethylene compositions was determinedby heating pellets of the polyoxymethylene compositions under nitrogenfor 30 minutes at a temperature of 259° C. The formaldehyde evolvedduring this time period was swept by a stream of nitrogen into atitration vessel containing a sufficient quantity of sodium sulfitesolution to absorb the formaldehyde. The formaldehyde reacted with thesodium sulfite to generate sodium hydroxide. The generated sodiumhydroxide was continuously titrated with hydrochloric acid to maintainthe original pH. The total volume of acid used was plotted as a functionof time. The total volume of acid consumed at 30 minutes wasproportional to the formaldehyde generated by the heatedpolyoxymethylene composition and was a quantitative measure of meltstability. The percent melt stability (referred to as TEF) wascalculated by the following formula:

TEF(%)=(V ₃₀ ×N×3.003)/S

where V₃₀=the total volume in mL of acid consumed at 30 minutes, N=thenormality of the acid, 3.003=(30.03 (the molecular weight offormaldehyde)×100)/(1000 mg/g), and S=the sample weight in grams.The results are shown in Tables 1 and 2 under the heading of “TEF”.

Discussion of Results

TABLE 1 Composition C1 C2 C3 C4 C5 C6 C7 POM 100 99.5 99 99.5 99 99.5 99Amide polymer 0.5 1 Polyamide 0.5 1 EVA 0.5 1 Physical Properties TEF(wt. %) 3.44 0.78 0.48 0.91 0.78 0.80 1.03

C2 to C7 in Table 1 show the effect on formaldehyde emissions whenvarious materials are used which are known to decrease formaldehydeemissions of polyoxymethylene compositions. C3 provides the lowestformaldehyde emissions at 0.48 weight percent when used at 1 weightpercent. C1 is polyoxymethylene without any additives and is used as acontrol.

TABLE 2 C8 C9 E1 E2 Composition POM 99.5 99 99.5 99 Amylopectin 0.5 1Glucan A 0.5 1 Physical Properties TEF (wt. %) 0.72 0.87 0.59 0.45

Table 2 shows the effect on formaldehyde emissions of polyoxymethylenecompositions in the melt state when two different polysaccharide basedmaterials are added to the composition. When amylopectin is added, theformaldehyde emissions is reduced relative to the control to 0.72 weightpercent. However, when poly alpha-1,3-glucan is added to thecomposition, there is a surprising further reduction in formaldehydeemissions to 0.59 weight percent. This is an improvement of at least 18percent relative to the use amylopectin at the same concentration and animprovement of more than 50 percent relative to amylopectin when bothmaterials are added at one percent to the polyoxymethylene composition.

Poly alpha-1,3-glucan, when added to polyoxymethylene at 0.5 weightpercent exhibits the lowest formaldehyde emissions of any materialtested at 0.59 weight percent.

TABLE 3 E3 E4 C10 C11 C12 Composition POM 99.25 99.25 99.25 99.25 99.25Soarnol A 0.05 0.05 0.05 0.05 0.05 Antioxidant 0.1 0.1 0.1 0.1 0.1Lubricant 0.15 0.15 0.15 0.15 0.15 Glucan A 0.45 Glucan B 0.45 Glucan C0.45 MC-1 0.45 MC-2 0.45 Physical Properties TEF (wt. %) 0.7 0.9 1.7 3.83.8

Table 3 shows the effect poly alpha-1,3-glucan particle size has on TEFemissions of a polyoxymethylene composition comprising an antioxidant, alubricant, and an ethylene vinyl alcohol copolymer. E3 and E4 have polyalpha-1,3-glucan particle sizes of less than 10 and 45 micronsrespectively. Both E3 and E4 exhibit TEF values of less than 1 percent.When the poly alpha-1,3-glucan particle size is greater than 50 micronsthe TEF values increase. C10 comprises a poly alpha-1,3-glucan having aparticle size of less than 180 microns (d90) and the TEF values are 1.7percent.

C11 and C12 are comparative examples in which the poly alpha-1,3-glucanis replaced with microcrystalline celluloses and the TEF values are atleast 200 percent greater than E3 and E4 which comprise the polyalpha-1,3-glucans disclosed herein. These results show that it is onlywhen specific polysaccharides are used in polyoxymethylene compositionsthat the resulting TEF values are less than about 1 percent.

What is claimed is:
 1. A polyoxymethylene composition comprising: a) atleast one polyoxymethylene polymer; b) about 0.1 to about 5 wt. % ofpoly alpha-1,3-glucan having a d90 particle size of 50 microns or less;c) optionally, at least one additive selected from the group consistingof nucleating agents, waxes, ultraviolet stabilizers, colorants,antioxidants, formaldehyde scavengers, lubricants, and mixtures ofthese; wherein said polyoxymethylene composition exhibits a formaldehydeemission of 1 weight percent or less when measured according to the TEFtest method; and wherein said particle size is measured according to ISO13320:2009.
 2. The polyoxymethylene composition of claim 1, wherein theformaldehyde emission is 0.7 weight percent or less.
 3. Thepolyoxymethylene composition of claim 1, wherein the formaldehydeemission is 0.6 weight percent or less.
 4. The polyoxymethylenecomposition of claim 1, wherein the at least one additive is present. 5.The polyoxymethylene composition of claim 4, wherein the additivecomprises a nucleating agent selected from the group consisting oftitanium oxides, boron compounds, silica, silicates, montmorillonite,calcium carbonate, valentinite, pyrophyllite, dolomite,melamine-formaldehyde condensates, phyllosilicates, talc, sulfates,carbonates, terpolymers of trioxane, and mixtures of these.
 6. Thepolyoxymethylene composition of claim 4, wherein the additive comprisesa formaldehyde scavenger selected from the group consisting of hydantoincompounds, imidazole compounds, and mixtures of these.
 7. Thepolyoxymethylene composition of claim 4, wherein the additive comprisesan antioxidant selected from hindered phenol antioxidants.
 8. Thepolyoxymethylene composition of claim 4, wherein the additive comprisesa lubricant.
 9. The polyoxymethylene composition of claim 1, wherein:the polyoxymethylene polymer has a melt flow rate of from about 0.5 g/10min. to about 100 g/10 min. when measured according to ISO
 1133. 10. Thepolyoxymethylene composition of claim 1 wherein the polyoxymethylenepolymer is a copolymer.
 11. The polyoxymethylene composition of claim 1wherein the polyoxymethylene polymer is a homopolymer.
 12. An articlecomprising the polyoxymethylene composition of claim
 1. 13. The articleof claim 12 in the form of gears, toys, cigarette lighter bodies,writing pen bodies, conveyor belt parts, safety restraint parts, carinterior parts, automotive fasteners, retractors, sliding members,snap-fit buckles, and zippers.
 14. A process of making apolyoxymethylene composition comprising the step of mixing: a) at leastone polyoxymethylene polymer; b) about 0.1 to about 5 wt. % of polyalpha-1,3-glucan having a d90 particle size of 50 microns or lessmeasured according to ISO 13320:2009; c) optionally, at least oneadditive selected from the group consisting of nucleating agents, waxes,ultraviolet stabilizers, colorants, antioxidants, formaldehydescavengers, lubricants, and mixtures of these; to prepare apolyoxymethylene composition, wherein said polyoxymethylene compositionexhibits a formaldehyde emission of 1 weight percent or less whenmeasured according to the TEF test method.